Safety device for an explosive fuze



Dec. 5, 1967 R. w. HEINEMANN 3,

SAFETY DEVICE FOR AN EXPLOSIVB FUZE Filed June 28, 1 66 FIG-2 INVENTOR.

Roberf W. Hein emann United States Patent 3,356,028 SAFETY DEVICE FOR AN EXPLOSIVE FUZE Robert W. Heinemann, Dover, N.J., assignor to the United States of America as represented by the Secretary of the Army Filed June 28, 1966, Ser. No. 562,437 4 Claims. (Cl. 10279) ABSTRACT OF THE DISCLOSURE A spring-loaded dash-pot adapted for separable engagement with a spring-loaded revolvable arming rotor of the fuze.

This invention relates to a safety device for use in a fuze of an explosive apparatus such as a centrifugally activated grenade and the like.

In the past, it has been found that explosive devices such as centrifugally activated grenades and the like may be accidentally armed during manufacture or merely by handling the device. This is due to the fact that the centrifugal force necessary to activate such a device is not required for any sustained period of time and is very slight indeed. As a result, personnel are subject to potential dangers, injuries and death if such grenades are subject to slight spin.

The potential hazards inherent in such a grenade are primarily due to the fuze which is armed merely by spinning under certain conditions. The conventional fuze for such a grenade is provided with a safety device in the form of a lock weight which is held in separable engagement against a rotor by means of a sensitive spring. As the grenade is revolved to any great degree, the inherent force generated in the direction away from the center of rotation functions to force the safety device out of engagement with the rotor thereby allowing the fuze to arm itself quite easily. What is needed in the art is a safety device which will not allow the fuze to arm until a predetermined degree of spin has been achieved for a sustained period of time.

It is therefore an object of this invention to provide a safety device of improved construction for use in the sustained arming of a fuze of a centrifugally activated grenade.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of the safety device of this invention in position against the rotor of a conventional fuze.

FIG. 2 is an enlarged fragmentary view of the safety device of FIG. 1.

FIG. 3 is a cross-sectional view of a further embodi ment of the safety device.

Similar numerals refer to similar parts throughout the several views.

As shown in FIG. 2, the device in the form of an improved air dash-pot is provided with a base 11 having an aperture 12 within which a porous diaphragm 13 is mounted. A hollow cylinder 14, of open end construction, is secured to the base 11, preferably in axial alignment with the aperture 12. A helical spring 15 is housed in the hollow cylinder 14 in supporting position against the base 11 and is adapted to receive, in abutting engagement, a solid cylindrically shaped lock-weight 16 which is insertably mounted within the hollow cylinder 14. In preferred embodiment, the cylinder 14 is made of Teflon or other 3,356,028 Patented Dec. 5, 1967 "ice frictionless equivalent such as polyethylene and the lock- Weight 16 forms a snug but slidable fit with the cylinder 14.

Referring again to FIG. 2, the device is inserted into the accommodating space of the fuze in such a manner that the base 11 is secured in position against the overlay 17 of the fuze, whereas the free end 18 of the lock-weight or solid cylinder 16 separably engages the locking space 19 of the spring-loaded revolva'ble rotor 21. The free space 22 of the cylinder 14, which is defined by the inner surface 23 of the base 11, the inner walls 24 of the cylinder 14 and the inserted end 25 of the cylindrically shaped lock-weight 16, is of a predetermined value in volume.

In operation, as the fuze, which houses the safety device, is spun at approximately 2400 revolutions per minute, the centrifugal force generated in the process tends to force the solid cylindrically shaped lock-weight 16 further into the hollow cylinder'14 against the spring 15. Due to this action, the spring 15 and the air in the free space 22 of the cylinder 14 are compressed and exert a compensating outward pressure against the inserted end 25 of the lock-weight 16. Such outward pressure is of a sufficient nature to prevent further free travel of the lockweight 16 into the cylinder 14. However, the porous diaphragm 13 is of such a nature as to allow the controlled bleeding of air from the free space 22 of the cylinder 14 and the controlled relaxation of the pressure exerted against the inserted end 25 of the lock-weight 16 by the air contained within the free space of the cylinder 14. As a result, the lock-weight 16 is allowed to progress into the hollow cylinder over a sustained period of time and the free end 18 thereof slowly separates from the rotor 21. As is apparent, the centrifugal force necessary to render the device operative and therefore the degree of spin required would largely depend on the compressive strength of the spring 15. If the fuze is not actuated for the predetermined period of time, preferably at 2400 revolutions per minute, the centrifugal force resulting from the spin will diminish and the outward pressure of the spring will tend to force the free end 18 of the lock-weight back into engagement with the rotor 21 of the fuze.

In a typical fuze, as shown, it may be necessary to utilize a plurality of the devices to secure the rotor in the safe or unarmed position. In such situation, although each of the devices will function on an individual basis, the overall action of the plurality of safety devices would be concurrent. When the proper degree of spin is obtained for the desired period of time, usually several seconds, each of the lock-weights will move outwardly under the influence of centrifugal force and will separate from engagement with their respective accommodating space on the rotor. As noted heretofore, the rotor is spring loaded and will immediately revolve to the armed position upon separation of the lock-weights.

In a further embodiment, as shown in FIG. 3, the solid cylinder lock-weight 16 is provided with a base 27 whose shape is dependent on the shape of the safety-catch or locking space 19 of the rotor 21. For instance, the base 27 may be flat in shape if the locking space 19, which is to accommodate the base 27, is relatively flat in shape whereas the base 27 may be pointed, round or triangular in shape if the locking space has a conforming shape. Further, an annular ring 28, may be secured to the base in such a manner that it circumscribes the solid cylindrically shaped lock-weight 16 in spaced relation thereto. When the device is in the assembled form, as shown, the annular ring 28 will form a tight but slidable fit with the hollow cylinder and the cylindrically shaped lock-weight 16. The base 27, solid cylindrically shaped lock-weight 16, and annular ring may be of one piece solid construction, without impairing the usefulness of the device, if this is more advantageous in the process of conventional manufacture.

A typical safety device for a conventional fuze of a centrifugally activated grenade has the following characteristics. The cylinder 14 has an outside diameter of about 0.153 inch and a wall thickness of about 0.010 inch, while the base 11 for such cylinder is approximately 0.194 inch in length and 0.168 inch in width with a thickness of 0.008 inch. The aperture 12 in this base 11 and the porous disc 13 are approximately 0.118 inch in diameter. Such disc 13 has been found to permit 1 cubic inch of air to escape from the cylinder 14 in 60 seconds per square inch of surface area of the disc. The cylinder 14' of the assembled device, in the operative state, with the lock-weight against the rotor of the fuze, contains about 0.0070 cubic inch of air within its confines. Further, the poro-us disc is designed to permit the lock-weight 16 to move a distance of 33 mils into the cylinder 14 in about 2 seconds at 2800 revolutions per minute. The spring 15 takes up approximately 0.008 inch of space in the compressed state in the assembled device and exhibits a strength of 2 to 3 pounds per square inch. Further, the lock-weight 16, which weighs between 1 and 2 grams, is about 0.131 inch in diameter and the base 27 for this unit is about 0.168 inch in width and 0.194 inch in length. The bottom surface of the base 27, in the preferred form, is concave and has a radius of 0.22 inch. Also, the annular ring 28 is approximately 0.070 inch in height.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. A centrifugally activated safety device for use in a fuze having a spring loaded revolvable arming rotor comprising:

a base having an aperture,

a porous diaphragm for the controlled bleeding of 'air mounted in said aperture,

a hollow cylinder of open end construction secured to said base in axial alignment with said aperture,

a helical spring in place in said hollow cylinder against said base, and

a solid cylinder one end of which is insertably mounted in said hollow cylinder and the other end of which is adapted for separable engagement with said rotor, said solidcylinder activated into movement into said hollow cylinder by centrifugal force, and. said movement incrementally controlled by the passage of air from said hollow cylinder through said porous diaphragm to the atmosphere.

2.. The device of claim 1 wherein said hollow cylinder is made of substantially frictionless material and said solid cylinder forms a snug, slidable fit with said hollow cylinder.

3. The device of claim 1 wherein a second base is secured to said free end of said solid cylinder and is adapted for separable engagement with said rotor.

4. The device of claim 3 wherein an annular ring is affixed to said second base and circumscribes in spaced relationship said solid cylinder, said ring functioning to align said hollow cylinder in relation to said solid cylinder.

References Cited UNITED BENJAMIN A. BOR CHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner. 

1. A CENTRIFUGALLY ACTIVATED SAFETY DEVICE FOR USE IN A FUZE HAVING A SPRING LOADED REVOLVABLE ARMING ROTOR COMPRISING: A BASE HAVING AN APERTURE, A POROUS DIAPHARGM FOR THE CONTROLLED BLEEDING OF AIR MOUNTED IN SAID APERTURE, A HOLLOW CYLINDER OF OPEN END CONSTRUCTION SECURED TO SAID BASE IN AXIAL ALIGNMENT WITH SAID APERTURE, A HELICAL SPRING IN PLACE IN SAID HOLLOW CYLINDER AGAINST SAID BASE, AND A SOLID CYLINDER ONE END OF WHICH IS INSERTABLY MOUNTED IN SAID HOLLOW CYLINDER AND THE OTHER END OF WHICH IS 